Sand blasting apparatus

ABSTRACT

A sand blasting apparatus with a cylindrically shaped, suction bell with a hollow interior, a workpiece holding disc which receives a workpiece and seals the open end of the bell, a slotted disc within the bell and above the workpiece holding disc in the abradent path for creating cyclonic downward flow and a vacuum system applying a vacuum to an opening near the open bell end to remove the abradent.

United States Patent [191 Schmall [451 Apr. 23, 1974 SAND BLASTING APPARATUS [75] Inventor: Karl Heinz Schmall, Baden-Baden, Oos, Germany 731 Assignee: gal/1101111511106111111101401111' Margrit schmall, Baden-Baden/Oos, Germany [22] Filed: Dec. 9, 1971 [21] Appl. No.: 206,370

[30] Foreign Application Priority Data 2,597,434 5/1952 Bishop et all. 51/12 2,907,200 10/1959 Roberts et a1. 51/8 x 5,142,942 8/1964 Celovsky 51/216 ND x 3,307,296 3/1967 Ashworth 51/8 3,545,996 12/1970 Duncan 51/319 x Primary ExaminerDonald G. Kelly Assistant Examiner-Howard N. Goldberg Attorney, Agent, or FirmCushman, Darby &

Cushman [57] ABSTRACT A sand blasting apparatus with a cylindrically shaped, suction bell with a hollow interior, a workpiece holding disc which receives a workpiece and seals the open end of the bell, a slotted disc within the bell and above the workpiece holding disc in the abradent path for creating cyclonic downward flow and a vacuum system applying a vacuum to an opening near the open bell end to remove the abradent.

5 Claims, 5 Drawing Figures PATENTEmma m4 sum 1 [IF 3 1 SAND BLASTING APPARATUS The invention relates to a sand blasting apparatus, especially for eroding or balancing electronic components, such as thick-film circuits supported by a holding means. Apparatuses of this type normally have protective walls positioned about the sand blasting nozzle, which walls are intended to prevent excessive spreading of the sand beyond that portion of the surface which actually is being processed. Moreover, in most cases there is further provided asuction means at the level of the structural component to be processed.

Known sand blasting apparatuses of this type primarily are disadvantageous in that reliable sealing of the sandblasting areacannot be obtained, this resulting in continual contamination of the processing facilities which contamination particularly also causes frequent troubles in operation. These disadvantages are the more apparent especially in automatic and semiautomatic processing machines wherein, on the one hand, a reliable sealing would be ofparticular importance in the interestof the mechanical parts provided for performing the automatic sequence of operations, and wherein, n the other hand, a satisfactory sealing heretofore could not be obtained in the first line because of the automatical supply and discharge (e.g.' by means of specialconveyor belts) of ,the components to be processed.

Accordingly, the invention is based primarily upon the object of providing a'sand blasting apparatus which prevents in optimum simple manner the egress of sand beyond the actual processing area. According to the invention, this object in the first line is solved in that the sand blasting nozzle and said holding means are eachdisposed on one of a pair of complementarycomponents which in their engaged condition enclose said nozzle and said holding means within a hollow space being substantially sealed relative to the exterior of said space, whereby it is of particular advantage when the nozzle is positioned within a suction hell or jacket having an opening'which isadapted to be closed by means of a disc. According to the invention, permits positive enclosing of the processing space with a simple configuration of the disc for the holding means and of the suction hell or jacket, without any additional cover means, whereby it is expedient that the suction bell or jacket opens downwardly and is provided with a rubber sealing ring with said disc being adapted to be pressed against said sealing-ring with engagement.

The inventionis particularly suited for use in apparatuses for the'successive erosionor balancing of components mounted on at least two holding means. If the holding means are each positioned on an associated one of a plurality of discs, and said individual discs are adapted to be moved sequentially beneath the bell or jacket, a positive sealing or isolation can-be obtained with automatic operation, whereby either the disc holding means may be loaded manually for every cycle of operation, or whereby sequential, autom atical charging of the holding means with automatic discharge after the processing operations is rendered possible. Precise positioning of the disc, being prior condition for the aspired positive sealing can be obtained in particularly good manner if according to the invention the discsare each arranged on a t'umtableso as to be adapted to be positioned beneath'the hell or jacket, or if there is-provided means for separately lifting said discs beneath the bell or jacket, whereby it may be advantageous if the turntable is lifted as a unit so that'thc respectively positioned disc is thereby brought into sealing engagement with the opening of the bellor jacket.

' According to the invention, the egress of sandcan be substantially completely prevented if a suction conduit or vacuum line is connected with the hollow space formed by the .components, and if the cross-sectional area of an air inlet and the degree of sealing between the components is selected such'that there exists a vacuum within the hollow space during the sand blasting operation when the components are engaged with each other, whereby it is advantageous if the direction of suction is aligned with the direction of the flow of sand by positioningthe air inlet in the upper portion of the bellor jacket and the suction conduit in the lower region of thebell or jacket. In this case,the air inlet may be provided either in the bell or jacket itself, or adjacent the holding meanson the disc.

If the air inlet isprovided with guide vanes such that the entering air is placed under turbulence to flow in the manner of a cyclon downwardly within thebellor jacket towards theoutlet, as an importantfeature of the invention there maybe provided thorough cleaningof the discand of the componentsper se from sand particles so that nosand residues are allowed toenterthe remainder of the apparatus after the separation be tween the bell or jacket and the disc.

"Hereby, the aspired cyclon-type turbulenceor swirling may be realized inparticularly effective and'simple manner if the guide vanes areformedby a disc orplate being provided with obliquely extending slots having point or radial symmetry. On the whole, the subject matter of the inventionhasto be seen in the novel individualfeatures and incombinations of the featuresemployed in the invention.

In' the following, preferred embodiments of the invention are explained in greater detail by referring to the drawings, wherein:

FIG. 1 is a partial sectional view of a suction bell or jacket having a disc-shaped support plate for the holding means of a thick-film structural component and structure for supplying a sand blasting stream for application to the workpiece and removing the stream from the hell or jacket; v

FIG. 2 is a pla n view of the disc or plate according to 7 FIG. 1;

FIG. 3 is a perspective view of a sand blasting apparatus comprising four discsor plates positionedon aturntable;

FIG. 4 is a sectional view of a modified suction bell or jackethavingguide vanes; and

' FIG. 5 is a plan FIG. 4.

According to FIGS. 1 and 2, a suction bell or jacket 1 comprises a sealing ring 2 with the edge 4 of a disc 3 being adapted to be pressedagainst suchsealing ring 2 with sealing engagement. A circuit substrate 6 of a thick-film circuit is fixedly positioned within a recess 5 of thedisc 3 and is correspondingly blasted by the sand blasting nozzle 7 after the disc 3 has been placed into the suction hell or jacket 1.

.Sand blasting nozzle 7 is fed anair stream enriched with .an abrasive powder such as aluminium oxide. This air stream comes from a mixing chamber 8 of known state of the art, which is supplied by a common air pressure pump system 9.

view of the guide vanes according to The disc 3 is mounted to a slide 10 of vertical movementto be moved up and down for change of substrate on the disc after abrading by the jet stream abradant and reloading the disc for the next abrading cycle.

For further explanation of a practically constructed arrangement, FIG. 3 illustrates a turntable 8 that can be turned by a definite angle, in the case shown of 90 degrees, positioned beneath the suction bell or jacket 1, which turntable has attached thereto four discs 3 each adapted to receive circuit substrates. The turntable 8 is adapted to be positioned beneath the suction bell or jacket in such manner that each of said discs 3 may be placed into the bell or jacket 1 when the turntable 8 is raised or lifted. Since the discs 3 are lifted jointly with the'tumtable 8, one single lifting mechanism only is required for the turntable instead of requiring one mechanism for each of the discs, this providing economical savings especially in the case of a greater number of discs.

FIG. 4 illustrates the suction bell or jacket 1 in combination with a vacuum line 13 and an air inlet 14. As shown at 15, the inflowing air is subdivided into separate air flows by slots 12 provided in a plate 11 and acting as guide vanes, which flows, after their egress from the slots 12, propagate in spiral fashion through the suction bell or jacket and flow out through vacuum line 13 after having reliably cleaned the circuit substrate 6 and the disc 3 from sand residues.

FIG. shows the symmetrical arrangement of the slots 12 formed in plate 11, which arrangement with a minimum amount of constructional expenditure ensures optimum cleaning by means of a plurality of individual air flows.

The air flown through the vanes, which may be performedby slots in a disc of same diameter as the bell as well as by small stripes of metal sheets or any other material arranged in such a manner that a guide is formed to direct the air stream to a helical stream. This stream velocities in the helical air movement may still exist, which is of negligible effect to the function of the suction bell system. it may, however, support the cleaning effect of the air stream at the level of the bottom disc and the substrate especially when the substrate is not a plane plate but has some height and forms of more complexity where the abradant tends to deposite in corners or edges. in these cases, the vanes are formed in such a way to direct parts of the air stream towards these corners to perform better cleaning process.

We claim:

1. Apparatus for sand blasting a workpiece comprismg:

a roughly cylindrically shaped suction bell having a hollow interior, a roughly circular bottom opening, a top opening and an opening adjacent said bottom opening,

a workpiece holding disc adapted for closing said bottom opening in a sealing relation with said workpiece within said hollow interior of said suction bell,

means mounted within said hollow interior and in communication with said top opening for receiving and applying a sand blasting stream to a workpiece in said hollow interior, including disc means mounted within said hollow interior adjacent said top opening and having a plurality of slots extending through said disc at an angle to the axis of said bell for creating cyclonic downward flow of the stream onto said workpiece, and

means connected to said bottom opening forapplying a vacuum to said opening adjacent said bottom opening to remove said stream.

2. The apparatus as in claim 1 wherein said slots are symmetrically disposed about said axis.

3. The apparatus as in claim 1 wherein said holding disc includes a sealing ring for engaging the periphery of said bottom opening and means for mountingsaid workpiece.

4. The apparatus as in claim 1 wherein said holding disc includes means for holding a plurality of workpieces.

5. The apparatus as in claim 1 wherein said removing means includes means for providing a vacuum within said hollow interior. 

1. Apparatus for sand blasting a workpiece comprising: a roughly cylindrically shaped suction bell having a hollow interior, a roughly circular bottom opening, a top opening and an opening adjacent said bottom opening, a workpiece holding disc adapted for closing said bottom opening in a sealing relation with said workpiece within said hollow interior of said suction bell, means mounted within said hollow interior and in communication with said top opening for receiving and applying a sand blasting stream to a workpiece in said hollow interior, including disc means mounted within said hollow interior adjacent said top opening and having a plurality of slots extending through said disc at an angle to the axis of said bell for creating cyclonic downward flow of the stream onto said workpiece, and means connected to said bottom opening for applying a vacuum to said opening adjacent said bottom opening to remove said stream.
 2. The apparatus as in claim 1 wherein said slots are symmetrically disposed about said axis.
 3. The apparatus as in claim 1 wherein said holding disC includes a sealing ring for engaging the periphery of said bottom opening and means for mounting said workpiece.
 4. The apparatus as in claim 1 wherein said holding disc includes means for holding a plurality of workpieces.
 5. The apparatus as in claim 1 wherein said removing means includes means for providing a vacuum within said hollow interior. 